Influence of the constitutive, conditional and inducible astroglia-derived tenascin-C ablation on synaptic function

神经胶质细胞来源的细胞外基质分子在发育过程中是神经元-神经胶质细胞相互作用的重要介质。最近，它们也被证明是损伤神经系统再生和成年哺乳动物突触可塑性的关键成分。这些细胞外基质分子之一是Tenascin-C，它在大脑发育的早期阶段由星形胶质细胞显著表达，在某些大脑区域也是如此。我们研究的目的是研究Tenascin-C如何影响幼年成年小鼠海马区的突触可塑性。这些研究将在结构性的、有条件的(在人GFAP启动子的控制下)和Tamofix en诱导消融的小鼠中进行。这些突变体的星形胶质细胞突起和树突形态的动态特征将在双光子显微镜下使用在人GFAP启动子控制下表达绿色荧光蛋白的转基因小鼠和脊髓的Dil标记来研究。常规的免疫细胞化学将被用来监测神经元和神经元亚群，以及它们相对于星形胶质细胞的相对比例和定位。电子显微镜将被用来立体地监测突触和相关的星形细胞突起的精细结构。这些细节和广泛的电生理测量将与CA1和CA3海马区相关的行为参数有关，如痕迹恐惧条件反射、模式完成、工作记忆和跳台回避，代表着星形胶质细胞-突触相互作用的更高水平。

Extracellular matrix molecules derived from glial cells have been shown to be important mediators of neuron-glia interactions during development. They have recently also been shown to be crucial ingredients in regeneration of the injured nervous system and in synaptic plasticity of adult mammals. One of these extracellular matrix molecules is tenascin-C that is prominently expressed by astrocytes at early stages of brain development and, in some brain regions, also in the adult. The aim of our study is to investigate how tenascin-C may affect synaptic plasticity in the hippocampus of young adult mice. These studies will be conducted with constitutively, conditionally (under the control of the human GFAP promoter) and tamofixen inducibly-ablated mice. The dynamic features of astroglial process and dendritic spine morphology will be studied in these mutants by 2-photon microscopy using transgenic mice expressing green fluorescent protein under the control of the human GFAP promoter and Dil labeling of spines. Conventional immunocytochemistry will be carried out to monitor neurons and subpopulations of neurons and their relative proportions and localization with respect to astrocytes. Electron microscopy will be used to stereologically monitor the fine structure of synapses and associated astrocytic processes. These finings and extensive electrophysiological measurements will be related to CA1 and CA3 hippocampus-associated behavioral parameters, such as trace fear conditioning, pattern completion, working memory and step-down avoidance, representing higher levels of astrocyte-synapse interactions.